Process of refining animal and vegetable oils



Oct. 28, 1941.

PROCESS OF REFINING ANIMAL AND VEGETABLE OILS Filed sept. 2, 1958 B. H. THURMAN Patented Oct. 28, 1941 man PROCESS 0F REFINING ANIMAL AND VEGE TABLE OILS Benjamin H. Thurman, Bronxville, N. Y., assigner to Refining, Inc., Nevada Reno, Nev., a corporation of Application September 2, 1938, Serial No. 228,201

(Cl. 26o-426) 14 Claims.

This invention relates to a process of refining vegetable oils and more particularly to such a process in which solvent extracted vegetable oils are continuously refined in the presence of said solvent.

In accordance with the present invention, it has been found that refining reagents may be continuously admixed directly with the miscella from vegetable oil extraction processes and that either partial or complete refining or a combination of the two may be continuously carried out without substantial loss of solvent and with markedly reduced refining losses. Preferably the refining process is made an integral part of the solvent extraction process, such that the entire extraction and refining operation is confined within a single closed system. The miscella from the extraction step may be first semi-refined to remove gums, coloring matter and other minor constituents therefrom prior to treating with a neutralizing reagent to completely refine the oil. This process provides for the recovery of valuable minor constituents such as phosphatides free from the reaction products due to neutralization. Alternatively, the miscella may be immediately admixed with a neutralizing reagent to form soap stock which is separated from the oil and solvent and which contains the minor constituents above referred to. Provision is made for removing substantially all of the solvent from the oil, minor constituents, or soap stock, and returning the same to the solvent extraction step after undesirable water. has been removed therefrom. The products such as gums, oil, and soap stock, are

therefore delivered from the process substantially free of solvent. In such a process the refining losses are substantially only the unavoidable and in the presence of the solvent to first remove gums and then free fatty acids.

Another object of the invention is to provide a process of continuously treating solvent extracted oils in the presence of the solvent to remove minor constituents other than free fatty acids therefrom and produce solvent-free minor constituents and semi-ref'lned or non-break oil.

Other objects and advantages of the invention will appear in the following description of the preferred embodiments of the invention given in conjunction with the attached drawing, which is a schematic diagram of apparatus capable of carrying out a complete solvent extracting and refining process.

Referring to the drawing, I0 indicates a source of supply such as a hopper for crushed seeds or beans, from which oil is to be extracted. The crushed material may move by gravity downwardly through a conduit II into a screw conveyor I2 which delivers the same into an extraction chamber I3 wherein the crushed material is treated with a solvent to remove oil. The screw conveyor I2 is preferably of the type which seals the chamber I3 from the hopper III, for example, a conveyor of the general type disclosed in my copending application Serial No. 157,410, filed Aug. 4, 1937. The crushed material moves slowly upwardly in the extraction chamber I3 by an elevating mechanism, for example, a helical rotatable screw member shown in dotted lines at I4 and driven from a suitable source of power through a pulley l5. Solvent is introduced into the extraction chamber I3 through a pipe I6 inlosses, that is, the losses due to removal of the impurities such as gums and free fatty acids.

It is, therefore, an object of thepresent invention to provide a continuous process of refining solvent extracted oil before removal of all of the solvent therefrom.

Another object of the invention is to provide a process of refining solvent extracted vegetable oils in the presence of the extracting solvent in which refining losses are minimized.

Another object oi' the invention is to provide a continuous process of extracting and refining vegetable oils in which the extraction and refining steps are carried on in a. single closed system to prevent loss of solvent.

Another object of the. invention is to provide a process of refining vegetable oils in which solvent extracted oils are treated in a closed system termediate the upper and lower portions of the chamber I3 and below the top of the pipe II so as to prevent solvent from backing up into the hopper Ill if the conveyor I2 fails to seal the chamber I3 against rearward ow of solvent therethrough. 'I'he solvent flows downwardly from the pipe I6 through the extraction chamber I3 countercurrent with the movement of the crushed material being extracted and the solvent takes up the oil of the crushed beans or seeds to form a miscella which is withdrawn through a pipe I1 and delivered into a storage chamber I8. A screen in the bottom of the extraction chamber I3, shown in dotted lines at I9, prevents the crushed material from being delivered in admixture with the miscella through the pipe Il. The residual material from which the oil has been extracted is elevated above the pipe I6 so that the solvent drains therefrom and is delivered through a closed chute 20 into a screw conveyor 2| which may be entirely similar to the screw conveyor I2. which screw conveyor 2| delivers the residual material into a vapor separating chamber 22 for removing solvent entrained with the residual material. as will be hereinafter described.

The miscella may -be continuously removed from the storage tank I3` through a pipe 23 by a pump 24 and passed through a heat exchange device 23 shown as a coil 23 positioned in a casing 21 through which any desired heating mediummaybepassed. The miscella maythenbel delivered into 'a vapor separating chamber 23 in which a part of the solvent may be separated in vapor form if the miscella contains more solvent than that desired in the refining process.

The miscella from which a portion of the solventy has been removed may then be withdrawn from the vapor separation chamber 23 through a'pipe 29 by a proportioning pump 33 and delivered through a heat exchange device 3| which may be similar to the heat exchange device 23. It the miscella in the storage tank I3 contains the desired amount of solvent for subsequent steps, the heat exchange device 23 and vapor separating chamber 29 may be by-passed by a pipe 33 by closing a valve 34 in the pipe 23, opening a valve 33 in the pipe 33, connecting the pipes 23 and 33; opening the valve 31 in the pipe 33 and closing the valve 39 in the pipe 29. The proportioning pump 30 will then draw the miscella directly from the storage tank I3 and deliver the same through the heat exchange device 3|. In either case the miscella may be deliveredv to a mixing device 39 wherein it is admixed in flow with a precipitating reagent for minor constituents such as gums and coloring matter. A proportioning pump 40 may withdraw precipitating reagent from a tank 4I and deliver a properly proportioned stream of the same to the mixer 33. The proportioning pumps 30 and 43 are shown as being driven by a variable speed motor 4I with a speed change device 42 positioned between the pumps. This proportioning mechanism is shown merely by way of example, and any other suitable type of proportioning mechanism capable of delivering accurately proportioned streams of miscella and precipitated reagent to the mixer 39 may be substituted therefor. The precipitating reagent causes the minor constituents to be thrown out of solution and the mixture of oil, solvent, precipitated minor constituents and any excess precipitating reagent is passed through a heat exchange device 43 anddelivered to a continuous centrifugal separator 44. The precipitated minor constituents and any excess precipitating reagent is separated from the oil and solvent in the centrifugal separator 44 and discharged as the heavy eilluent through a closed spout 43 into a screw conveyor 43 which may be of the same type as that shown at I2. The conveyor 43 delivers this material into a vapor separating chamber 41, similar to the vapor separating chamber 22. Solvents and, if desired, water are removed in vapor form from the separated material as hereinafter described.

The oil and solvent mixture is delivered as the lighter effluent from the centrifugal 44 through the pipes 43, 49 and 39 into a storage tank 5I. This mixture still contains free fatty acids and may be withdrawn from the tank I through pipes 52 and 53 by means of a proportioning pump 54 and passed through a heat exchange device 55 to a mixing device 53. A refining reagent may be withdrawn from the tank 31 and delivered by the proportioning pump 38 to the mixing device 33 wherein the refining reagent is mixed inow with the oil lndsolvcnt. Thereninlreagent neutraiixes the free fatty acids to form a mixture of oil, solvent and soap stock. This mixture may be passed through another heat exchange device 33 to a continuous centrifugal separator 33 wherein the soap stock is separated from the oil and solvent as the heavy emuent and discharged throughs closed spout 3l into a screw conveyor 32 which may be of the same type as the screw conveyor I2. The conveyor I2 delivers the soap stock into a vapor separating chamber 33 in which entrained solvent is separated in vapor form from the soap stock.

The refined oil and-solvent is delivered as the lighter eiiluent through the pipe 34 into the storage tank 33. The oil and solvent is continuously removed from the storage tank 33 by a pump 33 and passed through a heat exchange device 31 into a vapor separating chamber 31' in which the solvent is removed from the oil in vapor form.;

If it is not desired to recover the minor constituents separately from the soap stock, the entire minor constituent precipitating step can be omitted. For example, miscella from the extracting chamber I3 may be delivered directly to the storage -tank 3l through pipe II, pipe 33, pipe 49 and pipe 39. Sui'licient refining reagent may then be admixed with the miscella in the' mixer 33 to not only neutralize the free fatty acids but to precipitate the minor constituents, in which case the soap stock discharged from centrifugal 33 through the .spout 3l contains these minor constituents. If it is desired to remove a portion of the solvent prior to adding refining reagent and still omit the step of removing minor constituents, the miscella from the extraction chamber I3 may be passed through pipe I1 into the storage chamber I3, then removed from storage chamber I3 by the pump 24, and passed through the heat exchange device 23 and vapor separating chamber 23. The miscella from which a portion of the solvent has been removed may then be allowed to flow through the pipes 33, 49 and 30 into the storage chamber 3|, from which it is removed by the proportioning pump 34 and admixed with the refining reagent for the refining step.

If, on the other hand, a semi-refined or nonbreak oil is desired, rather than a completely refined oil, the minor constituent precipitating step may be employed and the :final refining step omitted. This can be done by delivering the semirefined oil discharged from the centrifugal separator 44 through the pipes 43, 49, 52, 39 and 34 directly to the storage tank 85, from which it may be removed by the pump 63 and delivered through the heat exchange device 31 to the vapor separating chamber 31. In any of the above operations, the final oil substantially free from solvent is removed from the vapor separating chamber 61' by means of a pump 10 and discharged from the process. In either case, in which a refining reagent is employed, the oil discharged by the pump lll is a completely refined oil substantially free of fatty acids, minor constituents, such as phosphatides, gums, resins and so forth, and substantially free of solvent. Where the semi-refining or minor constituent precipitating step only is employed, the. oil discharged by the pump 19 will contain free fatty acid, but may be classed 'as a semi-refined or non-break oil.

Various storage chambers I9, 5I and 63 may be small in size so' that the process is continuous.

These tanks are employed for the purpose of compensating for any slight variations in flow between different steps of the process, and in the case of the tank 65, for the purpose of isolating the centrifugal separator 66 from any vacuum which may be employed in the vapor separating chamber 61'. Since the level of liquid in these tanks may vary, they are vented back to the extraction chamber I3 through pipes 1I, 12 and 13, in order to prevent the building up of pressure in the various storage chambers and the loss of solvent to the atmosphere.

The vapor separating chambers 28 and 61' are employed to remove solvent from liquid materials, and may be'operated under vacuum or at any pressure appropriate to the solvent being employed, so that the solvent is substantially completely removed from the liquid material. These vapor separating chambers are connected by pipes 14 and 15 with a condenser 16 in which the vaporized solvent is cooled and condensed to liquid form. The vapor separating chambers 22, 41 and 63 are employed to remove solvent-entrained in solid material and may be substantially similar. The conveyor 2| seals the extraction chamber I3 and vapor separating chamber 22 from each other, so that different pressures may be employed therein. Similarly, the conveyors 46 and 62 seal the centrifugal separators 44 and 66 from the vapor separating chambers 41 to 63 respectively, so as to prevent any vacuum employed in the vapor separating chambers from reaching the centrifugal separators. The solvent vapors separated from the solid materials 'in the vapor separating chambers 22, 4,1 and 63 are likewise delivered to the condenser 16 through pipes 11, 18 and 19, respectively, connecting with pipe 14. If desired, the temperature and pressure conditions in the vapor separating chambers 22, 41 and 63 may be such that Water is also removed from the solid materials in vapor form and delivered to the condenser 16. This water vapor is also condensed in the condenser 16 and delivered along with solvent to a receiver 30. A vacuum may be maintained in the entire condenser and vapor separating chamber system by means of a vacuum pump 8| connected to the upper portion of the receiver 80. Since the solvents employed in extraction processes are usually immiscible with water, they can be separated by gravity in the receiver 8|). Water which collects in the lower portion of the receiver 80 may be withdrawn therefrom and discharged from the process by means of a pump 82. Condensed solvent for use in the extraction process may be withdrawn from the receiver 86 by means of a pump 83 and delivered through a heat exchange device 34 and pipe I6 back to the extraction chamber I3. Any make-up solvent necessary for the process can be introduced into the process through a pipe 85 connected to the receiver 36.

Various heat exchange devices 25, 3|, 43, 55, 59, 61 and 64 are employed for raising or lowering the temperature of the solvent and the various mixtures in the process, so that the required temperature for the desired operation can be secured in any portion of the process. Also, the various conveyors I2, 2|, 46 and 62, as well as the solvent extraction chamber I3 Iand the various vapor separating chambers 22, 28, 41, 63 and 61', may be provided with heating jackets (not shown) in order to heat the material therein or maintain a desired temperature of the material.

- Each of the vapor separating chambers 22, 41 and 63 is provided with a discharge conveyor cooling the discharged material before the same is contacted with the air.

The miscella coming from solvent extraction chamber I3 in most cases contains much more solvent than oil, usually being between approximately to 90% solvent. Since such large amounts of solvent are unnecessary in a refining operation, it is usually desirable to remove a portion of the solvent prior to performing the refining operations. Solvent extraction operations are ordinarily carried onrbelow the boiling point of the solvent, but it has been found that more efficient extraction takes place if the temperature in the extraction chamber is'elevated to a point just below the boiling point of the solvent. 'I'his can be accomplished by heating the conveyor I2 and the extraction chamber I3 and also by heating the solvent delivered into the extraction chamber by means of the heat exchange device 34. For efficient separation of solvent from the miscella in the vapor separating chamber 28, it is ordinarily desirable to heat the miscella in the heat exchange device 25 under pressure to somewhat above the boiling point of the solvent so that suiiicient heat may be imparted to the mixture to remove the desired amount of solvent in the vapor separating chamber 23. Some vapor formation in the heat exchange device 25 is usually desirable for this purpose. The amount of solvent left in the miscella before delivering the same to the subsequent refining steps will depend upon the nature of the oils extracted and the solvent employed, but usually will be in the neighborhood of a 1:1 mixture up to a 1:2 mixture by weight of oil and solvent. The temperature of mixing with the precipitating reagent in the mixer 39 can be controlled by the heat exchange device 3| and will also vary with the nature of the oil being treated and the amount and nature of the solvent in the miscella. Ordinarily this temperature will range between 70 F. up to just below the boiling point of the solvent. The precipitating reagent is added in amounts ranging between 1 and 10%, depending upon the amount of minor constituents in the oil. The preferred precipitating reagent is a 10% solution of boric acid, but other reagents, such as water, neutral, slightly acid or slightly alkaline solutions of salts such as alkaline metal salts, may be employed. The precipitating solutions cause such minor materials as phosphatides, resins, proteins, to be thrown out of solution along with coloring matter. The heating device 43 is employed to adjust the temperature to that found most suitable for separating the particular mixture formed, which temperature will also ordinarily be between approximately 70 F. and the boiling point of the solvent.` 'I'he heating device 43 also provides a short treating time which has been found to condition the mixture for centrifugal separation. y

The heating device 55 is employed to bring the oil and solvent to the temperature found most desirable for mixing with the refining reagent employed. No precise temperature of mixture applicable to. all oils and solvents can be given but the temperatures will ordinarily fall within thesame ranges as given for mixing the precipitating reagent with the miscella.. 'I'he preferred refining reagent is an aqueous solution of caustic,

although other alkalles such as caustic potash and alkali metal carbonates may be employed. Caustic soda, however, apparently has the best color reduction action. Sumcient refining reagent is employed to neutralize the free fatty acids of the oil and to provide an excess for reaction .with color impurities in the oil. The heating device 59 is then employed to condition the mixture for separation and for bringing the mixture to the temperature at which most emcient separation can be accomplished. This temperature will likewise depend upon the oil, amount of soapstock present therein. and the solvent employed.` The temperature for separation will usually fall between 70 F. and a temperature Just below the boiling point of the solvent. As the solvent reduces the viscosity of the oil throughout the process, lower temperatures may ordinarily be employed in all stages of the refining operation than can be employed in conventional refining processes.

'I'he refined oil is then heated in the heat exchange device 61 to a temperature at which substantially all of the solvent is vaporized from th oil in the vapor separating chamber 81.

It has been found that precipitating minor constituents or neutralizing free fatty acids in the presence of the extraction solvent almost entirely prevents the entrainment of neutral oil in the gums or soap stock separated from the oil. 'Ihere is a substantially complete separation between the aqueous phase containing the soap or other minor constituents and the solvent phase containing the oil. This is particularly true in the present process, where the precipitated materials such as gums or soap stock -are promptly separated from the oil and solvent after the reagents have been admixed therewith. Unless this separation is carried out promptly, there is a tendency for gums or soap stock to dissolve into the oil solvent phase so as toresult in incomplete separation. In the present process the precipitated materials are separated from the oil and solvent usually within five minutes after admixture therewith, and the entire process of extraction and refining requires but a short period of time. Also, it has been found that even a caustic reagent does not saponify any material portion of the neutral oil during the neutralization and separation steps. The process, therefore, substantially eliminates rening losses due to entrainment of neutral oil and to saponiflcation of neutralvoil, thus reducing the rening losses to almost an absolute minimum.

The preferred solvent employed in the above process is benzene, although it is possible to employ gasoline, dichloroethylene, and pentane. Furthermore, propane may be employed if the extraction and other steps are carriedout under pressure. Preferably, the centrifugal separators employed in the process are closed from the atmosphere to prevent loss of solvent, such that an entirely closed system is provided. While the yz invention has particular has particular utility in the refining of solvent extracted oils in the presence of the extraction solvent, other oils, for example those produced by pressing operations, or solvent extracted oils from which the solvent has been removed, can be admixed with proper proportions of solvent for the oil and subjected to the refining step or steps of the present invention.

a mixture of vegetable or animal oil and a solvent therefor. Also gravity separation steps, particularly continuous decantation in a closed system, may in certain cases be employed for separating the precipitated minor constituents or the soap stock from the oil-solvent phase.

While I havey disclosed the preferred embodiment of my invention, it is understood that the details thereof may be varied within the scope of the following claims.

I claim:

l. The method of producing refined vegetable oils, which comprises, extracting the oils by means of a solvent therefor, continuously mixing a refining reagent with saidoil in the presence of said solvent, continuously centrifugally separating foots produced by said refining reagent from said oil, and thereafter 'separating the solvent from the oil for re-use in the extraction step, said process being carried out in a closed system for preventing loss of solvent and admixture of air with the materials in said process.

2. The method of producing refined vegetable oils, which comprises, continuously extracting said oils with a solvent for the same to form a miscella, continuously mixing a stream of a precipitating reagent with said miscella to precipitate minor constituents contained therein, continuously centrifugally separating the precipitated materials from said miscella, thereafter admixing a stream of an alkali refining reagent with said miscella to produce soap stock, and continuously centrifugally separating the said soap stock from said miscella, said process being carried out in a closed system for preventing loss of solvent and admixture of air with the materials in said process.

3. The method of refining vegetable oils, which comprises, continuously admixing an alkali rening reagent with a mixture of said oil and a solvent therefor to form a mixture of oil, solvent and soap stock, thereafter continuously centrifugally separating said soap stock from said oil and solvent, and removing the solvent from said oil to produce a refined oil substantially free of impuritiesand solvent, said process being carried out in a closed system for preventing loss of solvent and admixture of air with the materials in said process.

4. The method of refining vegetable oils, which comprises, forming a stream of a mixture of said oil and solvent therefor, continuously mixing a stream of an aqueous alkali refining reagent with said mixture to produce a stream of a resultant mixture of oil, solvent and soap stock, delivering said latter stream to a centrifugal separator, continuously separating said resultant mixture into an aqueous phase containing said soap stock and a solvent phase containing refined oil, and removing said solvent from said refined oil.

5. The process of recovering refined animal and vegetable oils, which comprises, continuously extracting the oil from a material containing the same in an extraction chamber with a solvent for l said oil to form a miscella containing oil and sol- Vvent, withdrawing a stream of said miscella from `said chamber and continuously admixing therewith a stream of refining reagent which reacts with impurities in said oil to produce foots insoluble in said miscella, continuously delivering the resultant stream to a centrifugal separator, continuously centrifugally separating the foots from said miscella in said separator so as to deliver separate streams of foots and a mixture of 'I'he term miscella is employed herein to mean 75 oil and solvent, vaporizing solvent from said oil,

condensing the vaporized solvent and returning the condensed solvent to said extraction chamber, said process being carried out in a closed system for preventing loss of solvent and admixture of air with the materials in said process.

6. The process of recovering refined animal and vegetable oils, which comprises, continuously introducing material containing said oil into an extraction chamber, continuously introducing a stream of solvent into said chamber and admixing the same with said material to dissolve said oil, separately and continuously withdrawing a stream of miscella containing oil and solvent and a stream of the material from which the oil has been extracted from said extraction chamber, admixing a stream of refining reagent with said stream of miscella to form a mixture of oil, solvent, and precipitated impurities, continuously centrifugally separating said precipitated impurities from said oil and solvent, vaporizing the solvent from said oil and any solvent entrained in said impurities and in the material from which the oil has been extracted, condensing the vaporized solvent and returning the same to said extraction chamber, said process being carried out in a closed system out of contact with the air and said oil, solvent, and material being discharged to the air after said solvent has been removed therefrom while preventing entrance of Iair into said system.

7. The process of recovering refined vegetable and animal oils, which. comprises, continuously extracting said oils from material containing the same in a closed extracting chamber with a solvent for said oils to form a miscella of solvent and oil containing free fatty acids, withdrawing a stream of said miscella from said chamber and admixing therewith an aqueous alkaline refining solvent, continuously centrifugally separating foots produced by said refining reagent from said oil, thereafter separating the solvent from the oil for re-use in the extraction step, and maintaining said oil in a closed system when mixed with said solvent.

9.!The method of producing refined vegetable olls,` which comprises. continuously extracting said oils with a solvent for the same to form a miscella, continuously mixing a stream of a precipitating reagent with said miscella to precipitate minor constituents contained therein, con-` tinuously centrifugally separating the precipitated materials from said miscella, thereafter admixing a stream of an alkali refining reagent with said miscella to produce soap stock, continuously centrifugally separating the said soap stock from said miscella, continuously vaporizing said solvent from said oil, condensing said solvent and utilizing a stream of condensed solvent to extract additional oil.

10. The method of refining animal and vegetable oils, which comprises, forming a stream of a mixture of said oil and a solvent therefor, continuously mixing a stream of an aqueous alkali rening reagent with said stream of oil and solvent to produce a resulting stream of oil, solvent and soap stock, delivering said resulting stream to a centrifugal separator, continuously separating said soap stock from said oil and solvent, and thereafter removing said solvent from the refined oil.

11. The method of refining animal and vegetable oils, which comprises, forming a stream of a mixture of said oil and a solvent therefor, continuously mixing a stream of an aqueous alkali refining reagent with said stream of oil and solvent to produce a resulting stream of oil, solvent and soap stock, delivering said resulting streams to a centrifugal separator, continuously separating said soap stock from said oil and solvent, and thereafter removing said solvent from the refined oil, said process being carried out in a closed system for preventing loss of solvent and admixture of air with the materials in said process.

12. The process of refining vegetable and animal oils, which comprises, forming a stream of a mixture of said oil and a solvent therefor, admixing with said stream a stream of refining reagent capable of reacting with impurities in said oil to produce foots which are insoluble in said mixture of oil and solvent, continuously delivering the resultant stream to a centrifugal separator, continuously centrifugally separating said foots from said oil and solvent in said separator so as to deliver separate streams of foots and a mixture of oil and solvent, vaporizing solvent from said oil, condensing the vaporized solvent and mixing the condensed solvent with additional oil, said process being continuously carried out in a closed system for preventing loss of solvent and admixture of air with the materials in said process.

13. The method of refining animal and vegetable oils, which comprises, forming a stream of a mixture of said oil and a solvent therefor, continuously mixing a stream of an equeous alkali refining reagent with said stream of oil and solvent to produce a resulting stream of oil, solvent and soap stock, delivering said resulting stream to a centrifugal separator, continuously separating said soap stock from said oil and solvent, said method being carried out in a closed system and under pressure for preventing loss of solvent, and

thlereafter removing said solvent from the refined o 14. 'I'he method of refining animal and vegetable oils, which comprises, forming a stream of a mixture of said oil and propane as a solvent therefor, continuously mixing a stream of an aqueous alkali'reiining reagent with said stream of oil and solvent to produce a resulting stream of oil, solvent and soap stock, delivering said resulting stream to a centrifugal separator, continuously separating said soap stock from said oil and solvent, said method being carried out in a closed system and under pressure for preventing loss of said solvent, and thereafter removing said solvent from the refined oil.

BENJAIWIN H. 

